LTC4251/LTC4251-1/
LTC4251-2
Negative Voltage
Hot Swap Controllers in SOT-23
FEATURES
■
■
■
■
■
■
■
DESCRIPTIO
Allows Safe Board Insertion and Removal from a
Live –48V Backplane
Floating Topology Permits Very High Voltage
Operation
Programmable Analog Current Limit with Circuit
Breaker Timer
Fast Response Time Limits Peak Fault Current
Programmable Timer
Programmable Undervoltage/Overvoltage Protection
Low Profile (1mm) ThinSOT
TM
Package
The LTC
®
4251/LTC4251-1/LTC4251-2 negative voltage
Hot Swap
TM
controllers allow a board to be safely inserted
and removed from a live backplane. Output current is
controlled by three stages of current limiting: a timed
circuit breaker, active current limiting and a fast feedforward
path that limits peak current under worst-case catastrophic
fault conditions.
Programmable undervoltage and overvoltage detectors
disconnect the load whenever the input supply exceeds
the desired operating range. The supply input is shunt
regulated, allowing safe operation with very high supply
voltages. A multifunction timer delays initial start-up and
controls the circuit breaker’s response time.
The LTC4251 UV/OV thresholds are designed to match the
standard telecom operating range of – 43V to – 75V. The
LTC4251-1 UV/OV thresholds extend the operating range
to encompass – 36V to – 72V. The LTC4251-2 implements
a UV threshold of – 43V only.
All parts are available in the 6-Pin SOT-23 package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
ThinSOT and Hot Swap are trademarks of Linear Technology Corporation.
APPLICATIO S
■
■
■
■
■
■
■
■
Hot Board Insertion
Electronic Circuit Breaker
–48V Distributed Power Systems
Negative Power Supply Control
Central Office Switching
Programmable Current Limiting Circuit
High Availability Servers
Disk Arrays
TYPICAL APPLICATIO
GND
GND
(SHORT PIN)
R1
402k
1%
C1
10nF
R2
32.4k
1%
–48V, 2.5A Hot Swap Controller
R
IN
*
10k
500mW
3
5
V
IN
UV/OV
4
GATE
6
C
L
100µF
C
IN
1µF
+
LOAD
V
OUT
Q1
IRF530S
3
GATE
5V/DIV
LTC4251
TIMER SENSE
V
EE
C
T
150nF
2
1
R
C
10Ω
C
C
18nF
4
1
R
S
0.02Ω
2
425112 TA01
SENSE
2.5A/DIV
V
OUT
20V/DIV
–48V
*TWO 0.25W RESISTORS IN SERIES FOR
R
IN
ON THE PCB ARE RECOMMENDED.
U
Start-Up Behavior
1ms/DIV
425112 TA02
U
U
425112fa
1
LTC4251/LTC4251-1/
LTC4251-2
ABSOLUTE
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SENSE 1
V
EE
2
V
IN
3
6 GATE
5 UV/OV*
4 TIMER
(Note 1), All Voltages are Referred to V
EE
Current into V
IN
(100µs Pulse) ........................... 100mA
Minimum V
IN
Voltage ........................................... – 0.3V
Gate, UV/OV, Timer Voltage .......................– 0.3V to 16V
Sense Voltage ............................................– 0.6V to 16V
Current Out of Sense Pin (20µs Pulse) ............. –200mA
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range
LTC4251C/LTC4251-1C/LTC4251-2C ...... 0°C to 70°C
LTC4251I/LTC4251-1I/LTC4251-2I .... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
S6 PACKAGE
6-LEAD PLASTIC SOT-23
*UV FOR LTC4251-2
T
JMAX
= 125°C,
θ
JA
= 256°C/W
ORDER PART NUMBER
LTC4251CS6
LTC4251IS6
LTC4251-
1CS6
LTC4251-1IS6
LTC4251-
2CS6
LTC4251-2IS6
S6 PART MARKING
LTUQ
LTUR
LTQU
LTQV
LTK6
LTAAZ
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 2, 3)
SYMBOL
V
Z
r
Z
I
IN
V
LKO
V
LKH
V
CB
V
ACL
V
FCL
I
GATE
PARAMETER
V
IN
to V
EE
Zener Voltage
V
IN
to V
EE
Zener Dynamic Impedance
V
IN
Supply Current
V
IN
Undervoltage Lockout
V
IN
Undervoltage Lockout Hysteresis
Circuit Breaker Current Limit Voltage
Analog Current Limit Voltage
Fast Current Limit Voltage
GATE Pin Output Current
V
CB
= (V
SENSE
– V
EE
)
V
ACL
= (V
SENSE
– V
EE
)
V
FCL
= (V
SENSE
– V
EE
)
UV/OV = 4V, V
SENSE
= V
EE
, V
GATE
= 0V (Sourcing)
UV/OV = 4V, V
SENSE
– V
EE
= 0.15V, V
GATE
= 3V (Sinking)
UV/OV = 4V, V
SENSE
– V
EE
= 0.3V, V
GATE
= 1V (Sinking)
V
GATE
– V
EE
, I
IN
= 2mA
(Before Gate Ramp-Up)
LTC4251/LTC4251-2
LTC4251-1
LTC4251/LTC4251-2
LTC4251-1
LTC4251/LTC4251-2
LTC4251-1
LTC4251
LTC4251-1
●
●
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
I
IN
= 2mA
I
IN
= 2mA to 30mA
UV/OV = 4V, V
IN
= (V
Z
– 0.3V)
Coming out of UVLO (Rising V
IN
)
●
●
●
MIN
11.5
TYP
13
5
0.8
9.2
1
MAX
14.5
2
11.5
60
120
300
80
UNITS
V
Ω
mA
V
V
mV
mV
mV
µA
mA
mA
V
V
V
V
V
V
V
V
40
80
150
40
50
100
200
58
17
190
12
0.5
3.225
2.420
2.925
2.160
0.30
0.26
V
GATE
V
GATEL
V
UVHI
V
UVLO
V
UVHST
V
OVHI
External MOSFET Gate Drive
Gate Low Threshold
UV Threshold High
UV Threshold Low
UV Hysteresis
OV Threshold High
●
10
3.075
2.300
2.775
2.050
V
Z
3.375
2.540
3.075
2.270
5.85
5.86
6.15
6.17
6.45
6.48
425112fa
2
U
V
V
W
U
U
W W
W
LTC4251/LTC4251-1/
LTC4251-2
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 2, 3)
SYMBOL
V
OVLO
V
OVHST
I
SENSE
I
INP
V
TMRH
V
TMRL
I
TMR
PARAMETER
OV Threshold Low
OV Hysteresis
SENSE Input Current
UV/OV Input Current
Timer Voltage High Threshold
Timer Voltage Low Threshold
Timer Current
Timer On (Initial Cycle, Sourcing), V
TMR
= 2V
Timer Off (Initial Cycle, Sinking), V
TMR
= 2V
Timer On (Circuit Breaker, Sourcing), V
TMR
= 2V
Timer Off (Cooling Cycle, Sinking), V
TMR
= 2V
LTC4251/LTC4251-1
CONDITIONS
LTC4251
LTC4251-1
LTC4251
LTC4251-1
UV/OV = 4V, V
SENSE
= 50mV
UV/OV = 4V
●
●
●
●
ELECTRICAL CHARACTERISTICS
MIN
5.25
5.61
TYP
5.55
5.91
0.60
0.26
MAX
5.85
6.21
UNITS
V
V
V
V
µA
–30
–15
±0.1
4
1
5.8
28
230
5.8
0.7
1
±1
µA
V
V
µA
mA
µA
µA
µs
µs
t
PLLUG
t
PHLOG
UV Low to GATE Low
OV High to GATE Low
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to V
EE
unless otherwise
specified.
Note 3:
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
TYPICAL PERFOR A CE CHARACTERISTICS
2000
1800
1600
1400
I
IN
(µA)
I
IN
vs Temperature
V
IN
= (V
Z
– 0.3V)
1000
I
IN
(mA)
1200
1000
800
600
400
200
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G01
r
Z
(Ω)
U W
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
r
Z
vs Temperature
I
IN
= 2mA
I
IN
vs V
IN
T
A
= –40°C
100
T
A
= 25°C
10
10
9
8
7
6
5
T
A
= 85°C
T
A
= 125°C
1
4
3
0.1
0
2
4
6
8 10 12 14 16 18 20 22
V
IN
(V)
425112 G02
2
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G03
425112fa
3
LTC4251/LTC4251-1/
LTC4251-2
TYPICAL PERFOR A CE CHARACTERISTICS
V
Z
vs Temperature
14.5
I
IN
= 2mA
14.0
V
LKO
(V)
13.5
V
Z
(V)
10.0
9.5
9.0
V
LKH
13.0
12.5
12.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G04
Circuit Breaker Current Limit
Voltage V
CB
vs Temperature
60
58
56
54
120
115
110
50
48
46
44
42
40
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G07
100
95
90
85
80
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G08
V
FCL
(mV)
V
CB
(mV)
V
ACL
(V)
52
I
GATE
(Source) vs Temperature
70
UV/0V = 4V
TIMER = 0V
65 V
SENSE
= V
EE
V
GATE
= 0V
60
I
GATE
(mA)
I
GATE
(µA)
30
25
20
I
GATE
(mA)
55
50
45
40
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G10
4
U W
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
Undervoltage Lockout Hysteresis
V
LKH
vs Temperature
Undervoltage Lockout V
LKO
vs
Temperature
12.0
11.5
11.0
10.5
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G05
8.5
8.0
–55 –35 –15
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G06
Analog Current Limit Voltage V
ACL
vs Temperature
300
275
250
225
200
175
Fast Current Limit Voltage V
FCL
vs Temperature
105
150
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G09
I
GATE
(ACL, Sink) vs Temperature
400
UV/0V = 4V
TIMER = 0V
V
SENSE
– V
EE
= 0.15V
V
GATE
= 3V
350
300
250
200
150
100
5
0
–55 –35 –15
50
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G11
I
GATE
(FCL, Sink) vs Temperature
UV/0V = 4V
TIMER = 0V
V
SENSE
– V
EE
= 0.3V
V
GATE
= 1V
15
10
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G12
425112fa
LTC4251/LTC4251-1/
LTC4251-2
TYPICAL PERFOR A CE CHARACTERISTICS
V
GATE
vs Temperature
14.5
14.0
13.5
13.0
12.5
12.0
11.5
11.0
10.5
10.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G13
UV/0V = 4V
V
TMR
= 0V
V
SENSE
= V
EE
UV THRESHOLD (V)
V
GATEL
(V)
V
GATE
(V)
UV Threshold vs Temperature
2.55
2.50
2.45
LTC4251-1
6.25
V
UVHI
6.45
UV THRESHOLD (V)
OV THRESHOLD (V)
OV THRESHOLD (V)
2.40
2.35
2.30
2.25
2.20
2.15
2.10
2.05
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G16
I
SENSE
vs Temperature
–10
–12
–14
–16
–I
SENSE
(mA)
0.1
0.01
TIMER THRESHOLD (V)
I
SENSE
(µA)
–18
–20
–22
–24
–26
–28
–30
–55 –35 –15
UV/0V = 4V
TIMER = 0V
GATE = HIGH
V
SENSE
– V
EE
= 50mV
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G19
U W
V
UVLO
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
UV Threshold vs Temperature
3.375
LTC4251/LTC4251-2
3.275
3.175
3.075
2.975
2.875
2.775
–55 –35 –15
V
UVH
V
GATEL
vs Temperature
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G14
UV/0V = 4V,
V
TMR
= 0V,
GATE THRESHOLD
BEFORE RAMP-UP
V
UVL
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G15
OV Threshold vs Temperature
6.51
LTC4251
V
OVH
OV Threshold vs Temperature
6.41
6.31
6.21
6.11
6.01
5.91
5.81
5.71
V
OVLO
V
OVHI
LTC4251-1
6.05
5.85
5.65
5.45
5.25
–55 –35 –15
V
OVL
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G17
5.61
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G18
I
SENSE
vs (V
SENSE
– V
EE
)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
TIMER Threshold vs Temperature
V
TMRH
1.0
10
UV/0V = 4V
TIMER = 0V
GATE = HIGH
T
A
= 25°C
1.5
2.0
100
V
TMRL
1000
–1.5 –1.0 –0.5
0
0.5 1.0
(V
SENSE
– V
EE
) (V)
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G21
425112 G20
425112fa
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
